Embedding hidden auxiliary code signals in media

Abstract

Methods for embedding and reading auxiliary messages from image signals use embedded code signals modulated with the auxiliary message. These embedded ode signals may be used to convey hidden tracking codes in images, video and printed objects. The embedded code signals are embedded by varying characteristics of the image signal, including, for example, gray-level, reflective properties, photo-reactive properties, etc.

I claim: 
     
       1. A method of hiding an auxiliary message signal in an image signal comprising:
 receiving an auxiliary message signal comprising two or more message symbols; 
 associating the symbols with corresponding code signals comprising a plurality of elements, the plurality of elements having a mapping to corresponding locations in the image signal; and 
 adjusting the image signal at the corresponding locations according to a value of the message symbol, the code signal, and at least a characteristic of the image signal to produce an image signal with the auxiliary message hidden in the image signal. 
 
     
     
       2. The method of  claim 1  wherein the image signal is adjusted by varying reflective properties of the image on a physical medium. 
     
     
       3. The method of  claim 1  wherein the image signal is adjusted by varying photo-reactive properties of the image on a physical medium. 
     
     
       4. The method of  claim 1  wherein the image signal comprises video. 
     
     
       5. The method of  claim 1  wherein the mapping of the code signal has a random or pseudo-random property. 
     
     
       6. The method of  claim 5  wherein the image signal comprises video and the locations correspond to spatial locations within the video. 
     
     
       7. The method of  claim 6  wherein the adjusting comprises a non-linear adjustment according to a perceptibility function computed from an image characteristic. 
     
     
       8. A computer readable medium on which is stored instructions for performing the method of  claim 1 . 
     
     
       9. A method of reading a hidden an auxiliary message signal embedded in an image signal, where the auxiliary message signal comprising two or more message symbols, the message symbol values modulating embedded code signals, the embedded code signals having a plurality of elements mapped to location in the image signal, the method comprising:
 analyzing the image signal to determine an estimate of polarity of elements of the embedded code signals; and 
 extracting message symbol values from polarity of corresponding elements of the embedded code signals. 
 
     
     
       10. The method of  claim 9  including using an original image without embedded data to register the image with embedded data, and subtracting the original image from the registered image with embedded data. 
     
     
       11. The method of  claim 9  including evaluating the image signal to generate estimates of the polarity of the embedded code signal without using an original image not having the embedded data. 
     
     
       12. The method of  claim 9  wherein the image signal comprises video and the auxiliary data includes an identification code to track different copies of the video. 
     
     
       13. A computer readable medium on which is stored instructions for performing the method of  claim 9 . 
     
     
       14. A method of hiding an auxiliary message signal in an image signal comprising:
 receiving an auxiliary message signal comprising two or more message symbols; 
 associating the symbols with corresponding code signals comprising a plurality of elements, the plurality of elements having a mapping to corresponding locations in the image signal; and 
 at the corresponding locations, embedding the message symbols in the image signal according to a value of the message symbol and the code signal to produce an image signal with embedded auxiliary information, wherein the embedding is at least in part controlled as a function of a characteristic of the image signal to produce an image signal with the auxiliary message hidden in the image signal. 
 
     
     
       15. The method of  claim 14  wherein the image signal comprises video. 
     
     
       16. The method of  claim 14  wherein the value of the message symbol is used to set polarity of corresponding elements of the code signals for embedding into the image signal. 
     
     
       17. The method of  claim 14  wherein the code signals are maintained below a perceptibility threshold. 
     
     
       18. The method of  claim 14  wherein the code signals are created to have particular frequency characteristics. 
     
     
       19. The method of  claim 14  wherein the code signals are created to have particular frequency characteristics. 
     
     
       20. The method of  claim 14  wherein the embedding comprises a non-linear adjustment according to a function computed from an image characteristic.